This invention relates to a method and apparatus for performing the remote, real-time identification of the contents of containers by means of multiple radio frequency identification systems.
Radio Frequency ID (RFID) systems allow for the identification of objects at a distance and out of line of sight. They are comprised of transponders called radio frequency (RF) tags and RF interrogators (also called readers). The tags are smaller, sometimes as small as a grain of rice, less expensive than interrogators, and are commonly attached to objects such as product packages in stores. When an interrogator comes within range of an RF tag, it may provide power to the tag via a querying signal, or the RF tag may use stored power from a battery or capacitor to send a radio frequency signal to be read by the RFID interrogator.
RF tags may consist of single integrated circuits, circuits and antennae, or may incorporate more complex capabilities such as computation, data storage, and sensing means. Some categories of RFID tags include the following: passive tags that acquire power via the electromagnetic field emitted by the interrogator, semi-passive tags that respond similarly, but also use on-board stored power for other functions, active tags that use their own stored power to respond to an interrogator's signal, inductively coupled tags that operate at low frequencies and short distances via a coil antenna, single or dipole antenna-equipped tags that operate at higher frequencies and longer distances, read-write tags that can alter data stored upon them, full-duplex or half duplex tags, collision arbitration tags that may be read in groups, or non-collision tags that must be read individually.
RFID systems present a number of advantages over other object marking and tracking systems. A radio frequency interrogator may be able to read a tag when it is not in line of sight from the interrogator, when the tag is dirty, or when a container obscures the tag. RFID systems may identify objects at greater distances than optical systems, may store information into read/write tags, do not require a human operator, and may read tags hidden from visual inspection for security purposes. These advantages make RFID systems useful for tracking objects.
Generally, less expensive RFID systems have lesser capabilities. For instance, passive tags may have very low cost per unit, facilitating widespread use, but they also have limited range. RFID systems may also fail when applied to groups of objects, containers of multiple objects, or nested containers of objects. For shipping and warehousing of large containers on pallets, which often contain nested containers, inexpensive passive tags on individual objects may not provide adequate identification rates. Human manipulation of such objects may afford acceptable identification rates, but it also increases the cost of identifying each object. Active tags have greater range, but they may be impractical in many instances because of cost, shelf life, RF interference or other reasons. There is a need for a system that allows for the use of multiple tag types for groups of objects in potentially mobile containers that delivers a high read rate under a variety of conditions, at a distance, and at a reasonable cost. Such a system presents an advantage over prior art by surmounting compatibility issues presented by environments equipped with RFID systems of one type that need to process items tagged by a system of a different type.
U.S. Pat. No. 6,127,928 discloses an apparatus and method for a radio frequency document control system that enables the location of documents, such as office files, to be automatically and rapidly identified. The apparatus differs from this invention in a number of regards: the intermediate transceiver is not attached to a mobile container or described as operating while in motion; it requires a personal computer or other computation means to process the identity of documents; and its order of communication between transceivers does not allow for switched, efficient scanning of a container's content.
U.S. Pat. No. 6,529,446 discloses an interactive medication container or console that holds or otherwise organizes one or more medication vials or containers. The system automatically acquires information from memory strips on the vials or containers that is then made available to an external data processing system. It differs from this invention in several important regards: the medication container does not communicate via RFID with the external world, and the invention does not facilitate the rapid remote inventory of a mobile container.
U.S. Pat. Application No. 2002/0183882 A1 discloses a point of sale and delivery method and system using communication with remote computer and having features to read a large number of tags. The system resembles that disclosed in U.S. Pat. No. 6,529,446. It automatically acquires information from tags on the products within a container and then presents them to an external data processing system. It differs from this invention in several important regards: the external container does not communicate its contents via RFID with the external world. Instead, it uses, in one embodiment, an external RFID system to restrict access to the container. The invention does not provide the advantage of translating between incompatible RFID systems. The invention does not provide the advantage of effective remote inventory of clustered or nested containers via an external RFID system.